Method of improving optical quality of curved glass structures

ABSTRACT

Shaped glass structures, in particular to curved glass structures, having optically improved transmittance are provided along with methods of making such glass structures. Articles and methods described herein mask tube or reforming defects with help of refractive index-matching substances (e.g. optically clear adhesives) and/or additional glass layers. The articles and methods are applicable to any shaped glass, and is particularly useful for 3D-shaped parts for use in portable electronic devices.

This application claims the benefit of priority under 35 U.S.C. §119 ofU.S. Provisional Application Ser. No. 61/991,887, filed on May 12, 2014,the content of which is relied upon and incorporated herein by referencein its entirety.

FIELD

The present disclosure relates methods of making defect-free glassstructures, and in particular to making curved glass structures thathave near optical-quality to optical-quality surfaces.

BACKGROUND ART

There is a continued demand in a variety of consumer products for glassstructures that have high optical quality and precise shape along withthe strength that an thermally- or chemically tempered glass, such asGorilla Glass®, provides. Tubular glass shapes with circular ornon-circular, such as oval or square, cross sections are of particularinterest as they have applications in a number of fields, for example asthe exterior structure of electronic devices, such as telephones,electronic pads or other handhelds.

Glass quality is an essential attribute of such articles. In suchapplications, the glass must not only appear flawless, but must alsoprovide no distortion of the image transmitted from display and nouneven distortion of objects reflected from the glass surface. Ingeneral, such a high level of optical quality for a 3D shaped glass canonly be achieved through expensive and time-consuming polishingprocesses. However, polishing of noncircular designs is particularlydifficult due to the limited and asymmetric access to the internalsurfaces.

Presently, various tube reforming processes are being used or consideredfor achieving required shapes. These approaches present significantchallenges for reaching the necessary cosmetic requirements. First, thevast majority of commercially available tubes present an optical defectcalled ‘paneling’—an appearance of stripes or striations that runparallel to the tube direction. While not always noticeable in tubeform, they become particularly apparent to a naked eye in a moreflattened oval or squared cross section (a “sleeve”) form and/or whenthe glass is used as a display. Second, such reforming processes rely oncontact of some sort of tooling with glass at viscosities around theglass softening point. At these viscosities any contact is most oftendetrimental to the surface quality leading to nanometer to a micronscale surface distortions, imperfections or other variations thatapparent to a human eye. The present disclosure offers a solution of theoutlined problems, by masking tube or reforming defects with help ofoptically clear adhesives.

SUMMARY

Additional features and advantages of the disclosure are set forth inthe detailed description that follows, and in part will be readilyapparent to those skilled in the art from that description or recognizedby practicing the disclosure as described herein, including the detaileddescription that follows, the claims, and the appended drawings.

The claims as well as the Abstract are incorporated into and constitutepart of the Detailed Description set forth below.

All publications, articles, patents, published patent applications andthe like cited herein are incorporated by reference herein in theirentirety.

The present disclosure describes a method of improving optical qualityof glass articles used for consumer products by masking glass surfacedefects with help of refractive index matching substances (e.g.optically clear adhesives). The method is applicable to any shapedglass, and is particularly useful for 3D-shaped parts, and mostimportantly for tubes and sleeves.

The most clear example of the invention is usage of index matchingoptically clear adhesive (“OCA”)to direct bond the display to theinternal surface of sleeve glass enclosure. Combing it with externalpolishing of sleeve this enables achieving superior optical quality ofthe devise despite presence of surface defects introduced during sleeveproduction

Multiple approaches or their combination can be used to hide surfaceimperfections of a cover glass including direct bonding of a display;direct bonding of glass with high quality surface (e.g. Willow);laminating an index matching OCA film; or one side polishing combinedwith any of the above.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 provides examples of cross sections of “sleeves” or noncirculartubular structures that are embodied herein.

FIG. 2 is shows a xenon light shadowgraph illustrating “paneling”defects present on the vast majority of commercially-available glasstubes.

FIG. 3 is a shadowgraph of an externally polished, reformed glass sleevecoupon laminated on the left-hand half with and index matching OCA film(3M 8214®—4 mil) as compared to the unlaminated side (right) showingpaneling.

FIG. 4 is a picture of an externally polished glass sleeve part with theback panel removed for the illustration. A piece of 0.5 mm thick EAGLEXG® is glued to the inside of the sleeve (bottom section). A UV curableadhesive, VITRALITE® 7165, with refractive index of 1.51 is used toadhere the glasses together. The shadow from the sunlight highlights theadvantages of the combination of glasses and adhesive. Paneling andscratches (tooling marks during internal reforming process) are visibleon the bare part, but disappear in the bottom section where the fusiondrawn Eagle XG® glass is attached.

FIGS. 5A and 5B show not-to-scale designs of aspects of the glasssleeves described herein. FIG. 5A shows the first aspect, wherein thesleeve structure comprises an index-matching material and an electronicdevice. FIG. 5B shows the second aspect, wherein the sleeve structurecomprises optional index-matching materials, a second glass sheet, andan electronic device.

Cartesian coordinates are shown in certain of the Figures for the sakeof reference and are not intended as limiting with respect to directionor orientation.

DETAILED DESCRIPTION

The present disclosure can be understood more readily by reference tothe following detailed description, drawings, examples, and claims, andtheir previous and following description. However, before the presentcompositions, articles, devices, and methods are disclosed anddescribed, it is to be understood that this disclosure is not limited tothe specific compositions, articles, devices, and methods disclosedunless otherwise specified, as such can, of course, vary. It is also tobe understood that the terminology used herein is for the purpose ofdescribing particular aspects only and is not intended to be limiting.

The following description of the disclosure is provided as an enablingteaching of the disclosure in its currently known embodiments. To thisend, those skilled in the relevant art will recognize and appreciatethat many changes can be made to the various aspects of the disclosuredescribed herein, while still obtaining the beneficial results of thepresent disclosure. It will also be apparent that some of the desiredbenefits of the present disclosure can be obtained by selecting some ofthe features of the present disclosure without utilizing other features.Accordingly, those who work in the art will recognize that manymodifications and adaptations to the present disclosure are possible andcan even be desirable in certain circumstances and are a part of thepresent disclosure. Thus, the following description is provided asillustrative of the principles of the present disclosure and not inlimitation thereof.

Disclosed are materials, compounds, compositions, and components thatcan be used for, can be used in conjunction with, can be used inpreparation for, or are embodiments of the disclosed method andcompositions. These and other materials are disclosed herein, and it isunderstood that when combinations, subsets, interactions, groups, etc.of these materials are disclosed that while specific reference of eachvarious individual and collective combinations and permutation of thesecompounds may not be explicitly disclosed, each is specificallycontemplated and described herein.

Thus, if a class of substituents A, B, and C are disclosed as well as aclass of substituents D, E, and F, and an example of a combinationembodiment, A-D is disclosed, then each is individually and collectivelycontemplated. Thus, in this example, each of the combinations A-E, A-F,B-D, B-E, B-F, C-D, C-E, and C-F are specifically contemplated andshould be considered disclosed from disclosure of A, B, and/or C; D, E,and/or F; and the example combination A-D. Likewise, any subset orcombination of these is also specifically contemplated and disclosed.Thus, for example, the sub-group of A-E, B-F, and C-E are specificallycontemplated and should be considered disclosed from disclosure of A, B,and/or C; D, E, and/or F; and the example combination A-D. This conceptapplies to all aspects of this disclosure including, but not limited toany components of the compositions and steps in methods of making andusing the disclosed compositions. Thus, if there are a variety ofadditional steps that can be performed it is understood that each ofthese additional steps can be performed with any specific embodiment orcombination of embodiments of the disclosed methods, and that each suchcombination is specifically contemplated and should be considereddisclosed.

As noted above, the present disclosure is directed to methods of makingdefect-free glass structures, and in particular to making curved glassstructures that have near optical-quality to optical-quality surfacesare provided. Methods described herein mask tube or reforming defectswith help of refractive index matching substances (e.g. optically clearadhesives) or additional glass layers. The method is applicable to anyshaped glass, and is particularly useful for 3D-shaped parts, and mostimportantly for tubes and sleeves. The methods described provide thefollowing advantages: improved optical quality of a consumer productswith glass a cover; elimination of internal polishing step for thedevice assembly; enabling shapes where internal polishing is impossibleor impractical, e.g. sleeve shapes; enabling higher throughput, morecost effective or higher precision forming methods of making 3D shapedcover glass. For example, forming approaches where internal glasssurface is touched by tooling at low viscosity and therefor causingsurface degradation; in the particular case of tube reforming, enablingconventional tubes without superior surface quality to be used as afeedstock; and enabling larger display area or smaller bezel size of aconsumer electronics device.

As used herein, the term “sleeve” describes a three-dimensional, tubularglass substrate having a non-circular cross section. Generally, a sleevewill be somewhat oval in shape or somewhat rectangular in shape, whereinthe edges are rounded. In some embodiments, the sleeve will have atleast one face that is near optically or optically flat. FIG. 1 showsnon-limiting examples of cross sections of sleeves as used herein. Thesleeve may generally be composed of any glass composition that iscapable of being formed into the structure. In particular,borosilicates, alkali aluminosilicates, and other composition that canbe fusion drawn or pulled into tubes are of particular relevance. Thesleeves ideally have a thickness from about 0.3 mm to about 2.0 mm. Insome embodiments, the thickness of the tubes is constant, while in otherembodiments, the tubes may be thicker at key points, for example on thenarrow sides as shown in U.S. application Ser. No. 13/832,769, hereinincorporated by reference in its entirety.

The glasses used in the sleeves described herein can be tempered. Whileother glass compositions can be used, alkali aluminosilicates have theadded ability to be both thermally and chemically tempered. Chemicaltempering, or ion exchange, is well known in the art—e.g., U.S. Pat.Nos. 3,410,673 and 8,561,429, both of which are herein incorporated byreference in their entireties. The sleeves herein are ideally temperedto give the glass the added strength benefit for use of the sleeves inportable electronic applications.

While most of the embodiments herein are used particularly inapplication to sleeve glass enclosures, it is contemplated that the samemethod could be applied more widely, for example with the additionalstep of cutting the tubes in half to provide for 3D shaped cover glassparts.

Current tube reforming processes are being used or considered to try toachieve the required sleeve shapes for high end applications. However,these approaches present significant challenges for reaching cosmeticstargets. First, the vast majority of commercially available tubespresent an optical defect called ‘paneling’—an appearance of stripes orstriations that run parallel to the tube direction (FIG. 2). While notalways noticeable in tube form, they become particularly apparent to anaked eye in a sleeve form and/or when the glass is used as a display.Second, such reforming processes rely on contact of some sort of toolingwith glass at viscosities around the glass softening point. At theseviscosities any contact is most often detrimental to the surface qualityleading to nanometer to a micron scale surface distortions,imperfections or other variations that apparent to a human eye. Thepresent disclosure offers a novel solution to the outlined problems bymasking tube or reforming defects with help of optically clearadhesives.

In the past, surface polishing has generally been used to eliminatethese type of defects. However, polishing of noncircular designs isparticularly difficult due to the limited and asymmetric access to theinternal surfaces.

One of the principle ways used to analyze the surface quality of theglass tubing is through shadowgraphy. Shadowgraphy is an analyticalmethod wherein a bright light is passed through the tubing and theglass's shadow is analyzed for imperfections and/or paneling defects.While shadowgraphy does not have direct correlation with glass opticalperformance in a particular product, it is a very useful tool forhighlighting the differences in optical quality because it isparticularly good at enhancing the ability to detect even smallimperfections in the glass. Thus, it can be used as a surrogate methodto demonstrate improvements provided by embodiments described herein.

A first aspect, an example embodiment of which shown as 500 in FIG. 5A,comprises combining the tubular glass structure (or “sleeve”), 510, withan index-matching material or coating, 520, wherein the index-matchedcoating is located on the interior of the tubular glass structure, and,optionally, one or more electronic components, 540, located within boththe sleeve and the index-matched material. The index-matching material520 is a substance, usually a polymer, liquid, cement, adhesive, or gel,which has an index of refraction that closely approximates that of thesleeve 510. In some embodiments, the index-matching material 520 has anindex of refraction that within ±25%, ±20%, ±15%, ±10%, ±5%, or ±2.5% ofthe index of refraction of the sleeve. In particular, some embodimentshave an index-matching material 520 that has an index of refraction thatis within ±10% or ±5% of the index of refraction of the tubular glassstructure 510.

A second aspect, an example embodiment of which shown as 501 in FIG. 5B,comprises the tubular glass sleeve 510 with a second, interior glasslayer, 530, comprising a high quality flat or flexible glass inside thesleeve, optionally, one or more index-matching materials or coatings,520 and 550, and, optionally, one or more electronic components, 540,located within both glasses and the optional index-matched material. Insuch embodiments, the interior glass 530 can be designed to contact theinterior of the sleeve 510 in particular regions, such as along long orflat regions, or if made of a highly flexible, thin glass, such asCorning Willow® glass, may be designed to contact the entire interior ofthe sleeve 510. The sleeve 510 and interior glass 530 may be laminatedtogether or direct bonded with an adhesive, which may be theindex-matching material. In cases where the glasses are laminated, anadhesive 520 may be present between the glasses, which may be theindex-matching material 520. Alternatively, the glasses may be laminatedtogether through heating or other processes. In the case of bonding, thetwo glasses may be combined with an adhesive or a combination ofadhesives that are index matched or work in combination with theindex-matching material or coating.

When an interior glass 530 is present, the index-matching material 520and/or 550 may be present between the sleeve 510 and the interior glass(M_(sg)), between the interior glass 530 and optional electronic device540 within the sleeve (M_(gd)) (when present), or both. When presentbetween both, the index-matching materials 520 and 550 may be the sameor different, depending on the refractive indices of the variouscomponents. In some embodiments, the index of refraction ofindex-matching material M_(sg) is within ±10% or ±5% of the index ofrefraction of the sleeve. In some embodiments, the index of refractionof index-matching material M_(sg) is within ±10% or ±5% of the index ofrefraction of the interior glass. In some embodiments, the index ofrefraction of index-matching material M_(sg) is within ±10% or ±5% ofthe average of the index of refraction of the sleeve and the interiorglass. In some embodiments, the index of refraction of index-matchingmaterial M_(gd) is within ±10% or ±5% of the index of refraction of theinterior glass 530. In some embodiments, the index of refraction ofindex-matching material M_(gd) is within ±10% or ±5% of the index ofrefraction of the electronic device's display glass. In someembodiments, the index of refraction of index-matching material M_(gd)is within ±10% or ±5% of the average of the index of refraction of theinterior glass and the electronic device's display glass.

In addition to the index-matching aspect of coating, in someembodiments, the index-matching material 520 and/or 550 comprises asubstance that has additional beneficial properties. For example, theindex-matching material 520 and/or 550 may act as a laminating layerthat directly or indirectly increases the strength of the sleeve 510and/or prevents the sleeve 510 from shattering or coming apart whenexposed to damage. In some embodiments, the index-matching material 520and/or 550 may act as a cushioning or protective layer for anyelectronic components 540 within the sleeve 510. This can help toprevent the electronic components 540 from being damaged when the device500 or 501 is dropped and, in some cases, also lessen damage to thesleeve 510 by reducing interior stresses.

The index-matching coating 520 and/or 550 may comprise any material thatworks in the application—meaning, e.g., that not only does the materialmeet the necessary index of refraction limitations, but also otherproperties related to, e.g., thermal and photostability, adhesion,strength, transmittance, viscosity, glass transition, and/or color. Inparticular, UV curable, such as Vitralite 7565 with refractive index ofabout 1.51, or pressure sensitive adhesives are particularly useful inelectronics display applications. The coating can be from about 25 μm orgreater, for example, about 25 μm to about 200 μm. In some embodiments,the coating is >75 μm. In some embodiments, the coating is from >75 μmto about 200 μm.

Coatings 520 and/or 550 may be applied via any of the known means thatprovides an even covering and that works with the structure of thetubular glass structure 510. For example, the coating 520 and/or 550 maybe applied via dip coating, spray coating, spin coating, blading,brushing, vapor deposition, printing processes, or roll-to-rollprocesses. The coating 520 and/or 550 may be applied to the sleeve 510prior to insertion of any electronics 540, applied to the electronics540, which are then inserted into the sleeve 510, or may be applied tothe electronic device 500 or 501 after the electronics 540 have beenplaced within the sleeve 510 (for example, via an injection process).

Regarding the second, interior glass 530, it should be a high qualityglass substrate having a refractive index similar to the sleeve 510. Insome embodiments, the interior glass 530 has an index of refraction thatwithin ±25%, ±20%, ±15%, ±10%, ±5%, or ±2.5% of the index of refractionof the sleeve. In particular, some embodiments have an interior glass530 that has an index of refraction that is within ±10% or ±5% of theindex of refraction of the tubular glass structure 510.

The interior glass 530 thickness is ideally thin to prevent the glassfrom occupying the limited space within the sleeve, minimize opticaldistortion and allow for flexibility. In embodiments, the interior glass530 can have a thickness from about 30 μm (microns) to about 0.7 mm. Atthe lower end of the thickness range—from about 30 μm to about 200 μm,the glass 530 is flexible enough to be “wrapped” around the entireinterior of the sleeve. Glass products that could be used in such amanner include Corning's WILLOW® glass.

The interior glass 530 may be made from any glass composition and viaany process that meets the desired optical quality. Non-alkalicontaining glass compositions used in electronic display applicationsare particularly suited to this application—for example, Corning'sEAGLE® line of display glasses. However, in some embodiments, it may bedesirable to have a chemically tempered interior glass. In thosecircumstances, ion-exchangeable glass substrates may be used, such asCorning's GORILLA® glasses. When using alkali containing glasses,additional barrier layers may be incorporated into the device to prevention migration into the electronics. In cases where alkali poisoning is aconcern, thermally tempered non-alkali glass may also be used.thickness, optical quality—display IP, willow IP

Electronic components 540, such as electronic(LED/LCD) displays andadditional components, can be placed inside the tubular glass structure510 to produce an electronic device 500 or 501. In such embodiments, theindex-matching material 520 and/or 550 couples the electronic display540 to the sleeve 510 to reduce the appearance of paneling and otherdefects and, in some embodiments, enhance the light output from thedisplay. In addition to the display, other electronic components may beplaced in the sleeve 510, on either side of the index-matching material520 and/or 550, or in some embodiments, within the index-matchingmaterial 520 and/or 550. For example, transparent conductive oxides,metal meshes, and other touch-components know to those of skill in theart may be coated onto the sleeve prior to the addition of theindex-matching material 520 and/or 550. In some embodiments, waveguidestructures may be written into or on the sleeve 510 to give certaintouch or optical functionalities, such as shown in U.S. application Ser.No. 14/460,691, herein incorporated by reference in its entirety.

A third aspect comprises the combination of the approaches describedabove with additional techniques to further improve the perceivedsurface quality and hide surface imperfections on a sleeve. For example,in both the first and second aspects described above, embodiments maycomprise additional steps or components, such as polishing on theexterior or the interior, or additional exterior coatings, 560, such asanti-fingerprint, anti-smudge, scratch resistant, etc. coatings. In someembodiments, the interior is polished where the display will be locatedto minimize the amount of index-matching material needed. In embodimentswhere the exterior is polished, it is desirable to obtain a surface onthe glass sleeve that has a surface roughness (R_(a)) less than 1 nm andis free of defects having a size larger than 150 μm, 100 μm, or 50 μm.

In embodiments where the sleeve 510 has at least one planar “face” orlong side (FIGS. 1 and 5), the face should be very flat and free ofdistortions to provide an optically attractive surface. The flatness maybe obtained by the process used to make the sleeve or by polishing orother post-production processes. In addition to the imperfectionsdescribed above, the planar section should have a flatness better than±150 μm over a 10 mm×10 mm area or ±50 μm over a 25 mm×25 mm area asmeasured by a FlatMaster® tool.

Another aspect contemplates and electronic device 500 or 501 based onthe sleeve structures described herein. The electronic device 500 or 501comprises any of the previous aspects in combination with an electronicdisplay, such as a smartphone, tablet device or other portableelectronic device. In such embodiments, the index-matching coating 520or 550, when present, can bond the glass structure 530 to the electronicdevice 540 and, as noted previously may be index-matched to the sleeve510, the interior glass 530, or electronic display 540, or may have arefractive index that is an average of a combination of these. In caseswhere the interior glass layer 530 is not present, the coating mayfurther adhere the glass structure to the electronic device. As notedabove, in embodiments where the second glass substrate 530 is present,there may be one or more additional adhesives or coatings between thesecond interior glass and the electronic device or display, 550.

As noted above, the devices described herein may be produced via avariety of methods. The sleeve 510 can be produced via a number ofprocess, including by being directly drawn or by modification ofpreviously drawn circular tubing. Example methods can be found in U.S.Prov. Appl. Nos. 62/109,811, 62/107,598, 62/045,114, and 61/991,887, allof which are incorporated by reference in their entireties. Theindex-matching layer 520 can be placed in the sleeve prior to insertionof the interior glass 530 and/or the electronic device 540 or after,depending on the state of the material (i.e., liquid, solid polymer,etc.). Alternatively, the interior glass 530 and/or the electronicdevice 540 may be coated with the index-matching layer 520 and placed inthe sleeve 510. Similarly, where used, the index-matching layer 550 canbe place on either interior glass 530 and/or the electronic device 540,or inserted after placement of the interior glass 530 and/or theelectronic device 540. In some embodiments it is useful to use anindex-matching layer that is UV curable so that it can be inserted inliquid form to occupy the space between the interior glass 530 and/orthe electronic device 540, and then cured to provide a solid statelayer. In other embodiments, a polymer tape, such as apressure-sensitive polymer tape is advantageous due to the ability touse roll-to-roll processing or other means to apply the interiormaterials to the sleeve—this is particularly true where the interiorglass 530 is a flexible thin glass that can be rolled.

EXAMPLES Prospective Example 1

Usage of an index matching OCA to direct bond the display to theinternal surface of sleeve glass enclosure. Combing the display with anexternally polished sleeve enables achieving superior optical quality inthe devise despite the presence of surface defects introduced duringsleeve production. FIGS. 5 and 6 illustrate this example.

In FIGS. 3 and 4, Corning EAGLE XG®—0.1-0.7 mm thick is used to mimictypical LCD display. Pressure sensitive adhesive or UV curable adhesive,such as VITRALITE® 7565 with refractive index of about 1.51, can beused. UV curable adhesive is dispensed on the display, or a front glasssuch as EXG 0.5 to 0.2 mm thick, in a “h” or “x” pattern helping incorner feeding. Pressing is done via use of an iron-neodymium magnetduring UV insulation.

FIG. 5 clearly show the advantage of the present invention illustratinghow paneling (FIG. 1) disappear when the method is applied. FIG. 6 showshow another type of surface defect (called ‘center line’) is masked bythe method.

Although the embodiments herein have been described with reference toparticular aspects and features, it is to be understood that theseembodiments are merely illustrative of desired principles andapplications. It is therefore to be understood that numerousmodifications may be made to the illustrative embodiments and that otherarrangements may be devised without departing from the spirit and scopeof the appended claims.

1. An electronic device comprising: a glass sleeve structure having aninternal cavity, a first index of refraction, and a non-circular crosssection; an electronic device comprising a display, wherein theelectronic device is located in the internal cavity of the glass sleevestructure; an optional second glass structure between at least part ofthe glass sleeve structure and the electronic device, disposed on atleast part of the interior of the glass sleeve structure, and having asecond index of refraction, wherein the second index of refraction iswithin ±25% of the first index of refraction; and an index-matchingmaterial present between the glass sleeve and optional second glassstructure, wherein the index-matching material is disposed on at leastpart of the interior of the glass sleeve and has a third refractiveindex, wherein the third refractive index is within ±10% of the first orthe second index of refraction.
 2. The electronic device of claim 1,wherein the electronic device comprises a second glass structure and thesecond index of refraction is within ±10% of the first index ofrefraction and the third refractive index is within ±10% of the firstindex of refraction.
 3. The electronic device of claim 1, wherein theglass sleeve has a thickness from about 0.3 mm to about 2.0 mm.
 4. Theelectronic device of claim 1, wherein the second glass structure has athickness from about 30 μm to about 0.5 mm.
 5. The electronic device ofclaim 1, wherein the glass sleeve has been thermally or chemicallytempered.
 6. The electronic device of claim 1, wherein the glass sleevecomprises at least one planar surface area spatially coincident with thedisplay.
 7. The electronic device of claim 1, wherein the index-matchingmaterial comprises a polymer, liquid, cement, adhesive, or gel.
 8. Theelectronic device of claim 7, wherein the index-matching materialcomprises a polymer.
 9. The electronic device of claim 1, wherein theouter surface of the glass sleeve has a surface roughness (Ra) less than1 nm and is free of defects having a size larger than 150 μm.
 10. Acover article comprising: a glass sleeve structure having an internalcavity, a first index of refraction, and a non-circular cross section;an optional second glass structure between at least part of the glasssleeve structure and the internal cavity, disposed on at least part ofthe interior of the glass sleeve structure, and having a second index ofrefraction, wherein the second index of refraction is within ±25% of thefirst index of refraction; and an index-matching material presentbetween the glass sleeve and optional second glass structure, whereinthe index-matching material is disposed on at least part of the interiorof the glass sleeve and has a third refractive index, wherein the thirdrefractive index is within ±10% of the first or the second index ofrefraction.
 11. The cover article of claim 10, wherein the cover articlecomprises a second glass structure and the second index of refraction iswithin ±10% of the first index of refraction and the third refractiveindex is within ±10% of the first index of refraction.
 12. The coverarticle of claim 10, wherein the glass sleeve has a thickness from about0.3 mm to about 2.0 mm.
 13. The cover article of claim 10, wherein thesecond glass structure has a thickness from about 30 μm to about 0.5 mm.14. The cover article of claim 10, wherein the glass sleeve has beenthermally or chemically tempered.
 15. The cover article of claim 10,wherein the glass sleeve comprises at least one planar surface areaspatially coincident with the display.
 16. The cover article of claim10, wherein the index-matching material comprises a polymer, liquid,cement, adhesive, or gel.
 17. The cover article of claim 16, wherein theindex-matching material comprises a polymer.
 18. The cover article ofclaim 10, wherein the outer surface of the glass sleeve has a surfaceroughness (Ra) less than 1 nm and is free of defects having a sizelarger than 150 μm.
 19. A method of making the cover article of claim10, comprising combining: a glass sleeve structure having an internalcavity, a first index of refraction, and a non-circular cross section;an electronic device comprising a display, wherein the electronic deviceis located in the internal cavity of the glass sleeve structure; anoptional second glass structure between at least part of the glasssleeve structure and the electronic device, disposed on at least part ofthe interior of the glass sleeve structure, and having a second index ofrefraction, wherein the second index of refraction is within ±25% of thefirst index of refraction; and an index-matching material presentbetween the glass sleeve and optional second glass structure, whereinthe index-matching material is disposed on at least part of the interiorof the glass sleeve and has a third refractive index, wherein the thirdrefractive index is within ±10% of the first or the second index ofrefraction.
 20. A method of forming the electronic device of claim 1,comprising: forming a glass sleeve structure; coating: a. at least partof the interior of the glass sleeve with an index-matched coating andinserting the optional second glass structure into the glass sleeve; orb. at least part of the optional second glass structure with anindex-matched coating and inserting the optional second glass structureinto the glass sleeve; and inserting the electronic device in the cavityof the glass sleeve.